Etymologies

German (translation of Dutch Platduits, Low German) : platt, low, flat (from Middle Dutch plat, from Old French; see plate) + German Deutsch, German (from Middle High German diutsch, from Old High German diutisc, of the people; see teutā- in Indo-European roots).

(American Heritage® Dictionary of the English Language, Fourth Edition)

Borrowed from German Plattdeutsch. (Wiktionary)

Examples

Anyway the man explained they are Mennonites, they speak a language called Plattdeutsch, which is a dialect of German, they work as farmers and live apart from the general Paraguayan community in a colony, in this particular colony, there are 5000 of them, they have their own schools and hospitals, basically a country within a country.

Folks have been teaching him dialects, Plattdeutsch for the zone the British plan to occupy, Thur-ingian if the Russians happen not to drive as far as Nordhausen, where die central rocket works is located.

Aye, something of the sort,  the servant replied in Plattdeutsch, and later I learned that this dialect had been in full swing here, as well as the Frisian, for over a hundred years; the dikemaster and the overseers and the other landholders!